Recent ensemble forecasts from the Japan Meteorological Agency and global models point to overnight radiative cooling under variable high-pressure influence over the Kanto Plain, placing Tokyo’s May 20 minimum in the 18–22°C range with modest spread. Light winds and partial cloud cover are expected to limit extreme cooling, while the urban heat island at the Otemachi station raises baseline readings by 1–2°C relative to rural sites. Dew-point temperatures near 14–16°C further anchor the lower bound, and any increase in low-level moisture or stronger mixing could push the minimum above 22°C. Model consensus remains tight but sensitive to small shifts in steering flow or nocturnal cloud development, keeping probabilities evenly distributed across the mid-range bins. Updated JMA guidance and next model runs will clarify whether conditions trend toward the current 21°C peak or allow a dip into the upper teens.